Exemplary embodiments of the invention relate to an interlocking gearshift unit.
German patent document DE 10 2010 004 956 A1 discloses an interlocking gearshift unit for a motor vehicle drive train having a first clutch half and a second clutch half arranged so that they can slide relative to one another along an actuating direction in order to produce a connection with a fixed rotational relationship, wherein the first clutch half has a first engagement element and a second engagement element which can move with respect to the first engagement element.
Furthermore, an interlocking gearshift unit, in which two engagement elements of a clutch half are arranged so that they can move with respect to one another in a circumferential direction, is disclosed in the book “Freilaufkupplungen—Berechnung und Konstruktion”, Karl Stölzle, Sigwart Hart, Springer-Verlag, 1961, FIG. 157.
Exemplary embodiments of the invention are directed to cost-effectively increasing a shifting comfort of the interlocking gearshift unit.
Exemplary embodiments of the present invention are directed to an interlocking gearshift unit for a motor vehicle drive train having a first clutch half and a second clutch half, which are arranged so that they can slide relative to one another along an actuating direction in order to produce a connection with a fixed rotational relationship, wherein at least the first clutch half has at least one first engagement element and a second engagement element which can move with respect to the first engagement element.
Here, the engagement elements are arranged so that they can move in the circumferential direction. By this means, in a meshing operation of the interlocking gearshift unit, in which the connection with the fixed rotational relationship between the clutch halves is produced under differential speed, one of the engagement elements of the first clutch half can ease off along a circumference when it comes into contact with an engagement element of the second clutch half, thus enabling, in the case of an edge-to-edge contact or a flank contact with little overlap between teeth of the cushioning engagement element of the first clutch half and teeth of the engagement element of the second clutch half, an opposing force acting against the teeth of the engagement element of the second clutch half to be kept low. An edge is understood to mean an edge region of a tooth, in particular a chamfered edge region of a tooth. A flank is understood to mean a surface of a tooth arranged substantially parallel to the actuating direction and by means of which a torque can be transmitted following a completed meshing operation.
As, in the case of an edge-to-edge contact, only the tooth edges come into contact with one another instead of tooth flanks and, as a result, the contacting teeth only overlap to a small extent, the easing-off of one of the engagement elements and therefore the low opposing force can prevent the contact being broken once more, thus enabling the clutch halves to mesh further with one another until an overlap of the contacting teeth that is sufficient to transmit a torque is established. Because breaking of the edge-to-edge contact is prevented, grating is also avoided, thus avoiding vibrations and shocks in the meshing interlocking gearshift unit and therefore damage to the teeth. A kind of mechanical tooth gap sensor which, in a similar way to an electronic tooth gap sensor in motorsport gearboxes, allows meshing only in a region in which grating is ruled out, can be incorporated. By this means, a vibration and/or noise comfort of a shift of the interlocking gearshift unit can be increased without the use of additional electronics, thus enabling a shifting comfort of the interlocking gearshift unit to be cost-effectively increased. Further, a comfortable interlocking gearshift unit, which has low drag losses in the open running state compared with a friction gearshift unit, in particular a disc gearshift unit, can be provided, thus enabling a low-loss motor vehicle gearbox, for example, which has a high shifting comfort to be provided. An “engagement element” is understood particularly to mean an element having at least one tooth that is provided to engage in an interlocking manner in a tooth system of the engagement element of the other clutch half. A “circumferential direction” is understood particularly to mean a direction running around the actuating direction. Preferably, the actuating direction defines a direction of a longitudinal axis, around which the engagement elements are arranged so that they can rotate relative to one another. Here, the engagement elements are arranged substantially on a circular line around the bearing axis. The interlocking gearshift unit is preferably designed as a shiftable dog clutch or as a shiftable pawl brake. Preferably, the interlocking gearshift unit is used in an automatic planetary gearbox, thus enabling downshifts, in which the interlocking gearshift unit is closed, to be carried out particularly advantageously. In particular, “provided” is understood to mean specially designed, equipped and/or arranged.
Here, the first clutch half has a main body that is provided for transmitting a torque and to which the first engagement element is rigidly connected and with respect to which the second engagement element is rotatably arranged. This enables the second engagement element to be rotated about a certain angle relative to the first engagement element, as a result of which the torque transmission can be advantageously delayed or gradually reduced until a safe interlocking connection between the clutch halves is produced. Preferably, the second engagement element is arranged so that it can rotate about the bearing axis and therefore about the actuating direction relative to the first engagement element. Preferably, the main body and the first engagement element are formed in one piece with one another. In particular, “in one piece” is understood to mean molded in one piece.
According to the invention, the first engagement element has a multiplicity of blocking teeth and the second engagement element a multiplicity of fang teeth. By this means, in the meshing operation, the second clutch half first interacts with the second engagement element before interacting with the first engagement element, thus enabling the production of the connection with the fixed rotational relationship to be carried out more smoothly under differential speed. The fang teeth have the advantage that a probability of a direct meshing in the tooth gap is increased due to a large meshing tolerance. The meshing tolerance means a distance of the fang teeth from one another. Here, as a result of coming into contact with the teeth of the engagement element of the second clutch half, the fang teeth rotate until they rest against the blocking teeth or against a stop, thus enabling sufficient time to be made available to produce a reliable interlocking connection between the clutch halves. Further, it can be realized that torque is only transmitted between the clutch halves when the interlocking connection has been reliably made. A “blocking tooth” is understood to mean a tooth of the first rigid engagement element that blocks a meshing operation to a certain extent at its position. In particular, a “blocking tooth” is understood to mean a tooth of the first engagement element that forms an interlocking stop for a fang tooth for the purpose of transmitting torque and therefore preferably limits an angle about which the fang tooth can rotate relative to the blocking tooth and/or a freedom of movement of the fang tooth directed in the circumferential direction. The angle about which the fang tooth can rotate relative to the blocking tooth is preferably chosen to be sufficiently large that the meshing pawl halves are given enough time to produce an adequate overlap before the fang teeth rest against the blocking teeth and torque is transmitted. In particular, a “fang tooth” is understood to mean a tooth of the second rotatable engagement element which is provided to come into contact with the teeth of the engagement element of the second clutch half during the meshing operation before the teeth of the engagement element of the second clutch half come into contact with the blocking teeth. Preferably, a fang tooth is longer in the actuating direction than a blocking tooth. Ideally, a fang tooth is longer by an amount corresponding to the minimum overlap between a fang tooth and a tooth of the second clutch half. Particularly advantageously, the teeth on the second clutch half are exactly the same length as a fang tooth of the first clutch half.
In particular, it is advantageous when a fang tooth is arranged so that it can move in the circumferential direction between two blocking teeth. This enables a rotation of the clutch halves, which are connected with a fixed rotational relationship, to be prevented, thus enabling a so-called backlash play and therefore a knocking noise when changing load to be avoided.
Further, in order to provide an advantageous circumferential distance between two fang teeth, it is advantageous when the blocking teeth have a circumferential extension that is greater than a circumferential extension of the fang teeth. In the case of a tooth-on-tooth position, this enables reliable meshing of the teeth of the engagement element of the second clutch half in a next tooth gap after resolving the tooth-on tooth position, thus enabling a probability of meshing to be increased. In particular, a “circumferential extension” is understood to mean an extension in the circumferential direction.
Advantageously here, the fang teeth and the blocking teeth are arranged substantially on a circular line around the bearing axis. That is to say that the blocking teeth and the fang teeth are at substantially the same radial distance from the bearing axis. Particularly advantageously, teeth of the second clutch half are arranged on a circular line with substantially the same radius around the bearing axis.
Furthermore, it is advantageous when a circumferential distance between a fang tooth and a blocking tooth is substantially equal to an integral multiple of a circumferential extension of a tooth of the second clutch half, wherein the integral multiple also includes a multiple of one. This enables a backlash play in a meshed state of the two clutch halves to be prevented. A backlash play is understood to mean a gap between teeth of the first clutch half and teeth of the second clutch half in the meshed state, which leads to the two clutch halves knocking together when the direction of the load reverses.
In principle, both the blocking teeth and the fang teeth can be arranged in an axial or in a radial direction relative to the bearing axis. Likewise, the engagement element of the second clutch half can be arranged in an axial or in a radial direction.
Further, in order to save cost, it is advantageous when the blocking teeth are arranged on an inner circumference of the first engagement element and the fang teeth on a face side of the second engagement element, thus enabling the rotatable arrangement of the fang teeth and the rigid arrangement of the blocking teeth to be easily produced from a constructive point of view.
In order to arrange the engagement elements so that they can move elastically with respect to one another, in a particularly advantageous embodiment, the first clutch half has a damping unit that locates the second engagement element so that it can move elastically relative to the first engagement element in at least one circumferential direction. This enables a pre-defined starting position of the second engagement element relative to the first engagement element to be automatically established and maintained after releasing the connection with a fixed rotational relationship between the clutch halves. Further, this also enables an impact pulse on producing the connection with a fixed rotational relationship under differential speed to be damped, thus enabling shifting of the interlocking gearshift unit to be made particularly quiet. Further, the opposing force exerted by the second engagement element of the first clutch half on the engagement element of the second clutch half is limited, as a result of which the meshing together of the clutch halves is facilitated, as a frictional force between the two flanks which opposes a meshing movement is limited by the elastic mounting. Preferably, the damping unit locates the second engagement element elastically in both circumferential directions relative to the first engagement element, thus enabling grating to be reliably avoided when meshing under differential speed in combination with a direction reversal. Preferably, the damping unit has at least one elastic element that is repeatedly deformable without the element becoming mechanically damaged or destroyed thereby, and which automatically tries to return to the starting position, in particular after a deformation.
Further, the damping unit can have at least one spring, thus enabling, particularly advantageously, the second engagement element to be supported so that it can move elastically. The spring is preferably in the form of a helical spring. Basically, the damping unit can alternatively have a rubber element or similar as the elastic element. In a particularly advantageous manner, the elastic element or spring has a non-linear progressive spring characteristic.
In order to guarantee a reliable and rapid engagement of the interlocking gearshift unit, it is particularly advantageous when the engagement elements are additionally arranged so that they can slide elastically relative to one another along the actuating direction. As a result, in the case of the tooth-on-tooth position, one of the engagement elements can ease off elastically in an axial direction and buffer a meshing force which, when the tooth-on-tooth position is resolved, can then be used for complete meshing and therefore for terminating the meshing operation.
In addition, it is advantageous when the second clutch half has a main body that is provided for transmitting torque and at least one engagement element arranged so that it can slide elastically with respect to the main body along the actuating direction and which is connected to the main body with a fixed rotational relationship, thus enabling the engagement of the interlocking gearshift unit to be further improved in the case of the tooth-on-tooth position.
Further advantages can be seen from the following description of the figures. Four exemplary embodiments of the invention are shown in the figures. The figures, the description of the figures and the claims contain numerous characteristics in combination. Expediently, the person skilled in the art will also consider the features singly and combine them to form meaningful further combinations.